"""Simple captcha library, based on PIL. Monkey patch functions in this module

if you want something better...

:organization: Logilab

:copyright: 2009-2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.

:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr

:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses

"""

__docformat__ = "restructuredtext en"

from random import randint, choice

from cStringIO import StringIO

import Image, ImageFont, ImageDraw, ImageFilter

from time import time

from cubicweb import tags

from cubicweb.web import ProcessFormError, formwidgets as fw

def pil_captcha(text, fontfile, fontsize):

    """Generate a captcha image. Return a PIL image object.

    adapted from http://code.activestate.com/recipes/440588/

    """

    # randomly select the foreground color

    fgcolor = randint(0, 0xffff00)

    # make the background color the opposite of fgcolor

    bgcolor = fgcolor ^ 0xffffff

    # create a font object

    font = ImageFont.truetype(fontfile, fontsize)

    # determine dimensions of the text

    dim = font.getsize(text)

    # create a new image slightly larger that the text

    img = Image.new('RGB', (dim[0]+5, dim[1]+5), bgcolor)

    draw = ImageDraw.Draw(img)

    # draw 100 random colored boxes on the background

    x, y = img.size

    for num in xrange(100):

        draw.rectangle((randint(0, x), randint(0, y),

                        randint(0, x), randint(0, y)),

                       fill=randint(0, 0xffffff))

    # add the text to the image

    draw.text((3, 3), text, font=font, fill=fgcolor)

    img = img.filter(ImageFilter.EDGE_ENHANCE_MORE)

    return img

def captcha(fontfile, fontsize, size=5, format='JPEG'):

    """Generate an arbitrary text, return it together with a buffer containing

    the captcha image for the text

    """

    text = u''.join(choice('QWERTYUOPASDFGHJKLZXCVBNM') for i in range(size))

    img = pil_captcha(text, fontfile, fontsize)

    out = StringIO()

    img.save(out, format)

    out.seek(0)

    return text, out

class CaptchaWidget(fw.TextInput):

    def render(self, form, field, renderer=None):

        # t=int(time()*100) to make sure img is not cached

        src = form._cw.build_url('view', vid='captcha', t=int(time()*100),

                                 captchakey=field.input_name(form))

        img = tags.img(src=src, alt=u'captcha')

        img = u'<div class="captcha">%s</div>' % img

        return img + super(CaptchaWidget, self).render(form, field, renderer)

    def process_field_data(self, form, field):

        captcha = form._cw.session.data.pop(field.input_name(form), None)

        val = super(CaptchaWidget, self).process_field_data(form, field)

        if val is None:

            return val # required will be checked by field

        if captcha is None:

            msg = form._cw._('unable to check captcha, please try again')

            raise ProcessFormError(msg)

        elif val.lower() != captcha.lower():

            msg = form._cw._('incorrect captcha value')

            raise ProcessFormError(msg)

        return val